Stakhanov movement

In the de-occupied Donbas town of Yukom, a researcher who tried to prevent an ecological disaster threatening the region goes missing. Detective Leo Bagryany must find him, and even though he has psychic abilities, it will not be easy to do it. Too many strange things are happening in the city that was once Leo's home: the people of Yukom hear otherworldly sounds that have been dubbed the Groan of the Earth, people disappear for the first time, mutilated bodies are found on the outskirts, and graves are dug up in the cemetery. Who or what is really behind the gruesome murders? Is the mysterious secret society Stakhanov movement involved in this? And what was Stakhanov really looking for and what did he find deep underground almost a hundred years ago?